I had the issues written up in another thread but the thread wasn't about misfires, I figured i'd start a thread about just this problem.

I installed a hughes air gap intake along with plugs, wires, cap and rotor, and 02 sensor. Its throwing a p0135 heater circuit malfunction, i've checked the wiring and its good, fuse is good. Im going to replace the o2 sensor with one from the dealer. Would this cause misfires?

Its also showing p0302 and p0304. Ive checked the wires but im gonna check them again. The cap has brass contacts. The cap, rotor and wires were put back on the same as the old stuff came off. Plugs are gapped 0.040". Ive read the tsb for plug wires which is why im checking them again. Also it doesn't set the codes right when its started. After driving awhile it'll set the codes.
Could it be the 02 sensor causing the misfires? It is idling rough once it warms up. Almost wants to stall when stopped and it did stall once. Giving it gas makes it run decent again. The truck does pull alot better after 3000 rpm compared to the kegger although. It shifts at about 5000 rpm and pulls strong right to then. With the kegger the truck pulled good until 3500 rpm, then didn't do to much.
Thanks

 

Check plug wire routing, and firing order first. If that's good, make sure you don't have the injector connectors for 2 and 4 crossed. The engine is sequential fuel injection, so, it matters which one is plugged in where. Also, make sure the injectors are plugged in nice and tight, and the contacts are clean.

Check that stuff first, see what you find.

 

I swapped the plug wires with the old ones along with checking the injector connectors. I routed the new wires according to the tsb but it didnt help. the old wires only have 20000 kilometres on them, they'll work until i can order davis livewires 10mm wires, but it's running better and it isnt showing misfire codes anymore. With the other wires it started surging in o/d under light throttle. It isnt doing that anymore.

I have an o2 sensor on order at the dodge dealer here. It still has the p0135 code and a rough idle. If i bring the engine up to 800 rpm it runs good. I've been reading about it and apparently the o2 sensor can cause rough idle with the p0135 code. Does this sound right? I'm hoping this will solve the problem.

 

Quite possible. O2 sensor may be causing the engine to run too lean..... which will give you a random miss.

 

I bought an o2 sensor from the dodge dealer, it is an ntk sensor, however the part number is different from the other ntk o2 sensor i just changed with the intake. I changed it out and took the truck for a drive. At first i thought the problem was solved, then the check engine light came on. P0133 o2 sensor slow response bank 1 sensor 1. And misfire codes. The rough idle is still there. With the engine running i sprayed brake kleen around the intake manifold and the vacuum lines and connections looking for vacuum leaks and couldnt find any. I sprayed the bases of the injectors and nothing happened. I was wondering if maybe the injectors aren't seated proper, but wouldnt the engine rpm changed when i sprayed them? The injector connections seem to be good. I believe i have the plug wires routed proper. I put in champion copper stock replacement plugs gapped at 0.040, cap and rotor with brass connections. I replaced the engine coolant temp sensor with a napa part because the original broke when i removed it. Could this be causing problems? I'm running out of ideas. I also noticed the coolant temp the is higher than it used to be. The needle is about a needle width away from the middle mark (100 degrees celcius). Is this normal range? I think im gonna try bleeding the coolant system again. Thanks

 

To rule out O2 sensor causing miss, unplug it, go for a drive. See if the miss is gone.

New temp sensor may be reading slightly different from the old sensor, as the PCM and the gauge in the dash both get their cue from the same one.

 

I unplugged the o2 sensor and went for a 5 minute drive and it still misfires on cylinder 2 and 4 . I pulled all the spark plugs and they are covered in black soot. Would the IAT sensor mounted in the air cleaner pipe cause it to run so rich?

 

Is it just 2 and 4 that are sooty? Or is it all of them?

Might be time to test your injectors.

 

All of them are like that. How do i test the injectors? Fuel pressure is right around 49 psi

 

Fuel pressure is correct.

Wonder why it wants to run so rich....... Under normal circumstances.... I would just you have swap the injector next to the cylinder that is misfiring.... but, as you have two cylinders right next to each other misfiring........ and, coincidentally, at the end of the fuel rail, furthers from where fuel comes in.......

Pull the fuel rail, and all the injectors. Keep track of which injector goes where. (write on 'em with a sharpy if you have to.) blow all the crap out of the fuel rail, and then swap the 2/4 injectors with 1/3. Put it back together. See if your miss moves.

While they are off, might want to ohm check all your injectors. (should be right about 12 ohms)

If none of that makes any difference, get a noid light. Most auto parts stores should have 'em. Check and see if the PCM is actually pulsing the 2/4 injectors.